Idrija UNESCO
Global Geopark
IDRIJA UNESCO GLOBAL GEOPARK
The Idrija Geopark is a world of solitary trails, wild ravines, lush forests, and a rich natural and cultural heritage. Explore it through VIRTUAL PANORAMAS.
What Is a Geopark
A geopark is an area with extraordinary geological and other natural characteristics and landmarks in which its local populace undertakes a concerted effort to protect the area’s natural environment and spread awareness of its rare and special features. The geopark, in collaboration with the local people and tourist service providers, uses the area’s heritage and storied past to organize activities and develop various (geo)tourism products to encourage the development of rural areas. All the activities in the geopark are carried out in accordance with the rules of its thematic network and in harmony with the other members of the European Geoparks Network, which allows for a united development of all members.
Main geopark objectives:
- protecting and preserving geological and other natural heritage
- educating and interpreting natural and cultural heritage
- collaborating with local tourist service providers and local communities
Idrija UNESCO Global Geopark
The Idrija Geopark, which covers the entire area of the Municipality of Idrija, extends over an area of 294 km2 in western Slovenia, in the hills of Idrija and Cerkno. Because of its unique position at the crossroads of the Alps and the Dinarides, it represents a clear transition from subalpine to karst terrain with incredible diversity: deep dells below high karst plateaus with peaks offering scenic panoramas from the Julian Alps to the Adriatic Sea.
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Geomorphology
The area of the Idrija Geopark is characterized by an extremely diverse geomorphology with high karst plateaus that lack surface watercourses, but abound with caves, ravines, sinkholes, and other karst phenomena. These vast karst plateaus are situated at an elevation of 650 to 800 (some even 1,100) meters above sea level, and are divided by narrow and deep river valleys. In the areas surrounding their confluences or wide rocky riverbanks, the rivers have created good conditions for settlements: Idrija at the confluence of the Idrijca and Nikova rivers, Spodnja Idrija at the confluence of the Idrijca and Kanomljica rivers, and Idrijska Bela at the confluence of the Idrijca and Belca rivers. A remarkable feature of the Idrija region is the Idrija fault, which divides the area of the Idrija Geopark in half in the direction from the southeast to the northwest. Along the fault, the river Kanomljica has shaped one of the most beautiful valleys of the Idrija region. The high peaks above the valleys and karst plateaus (Javornik, Špičasti Vrh, Čelkov Vrh, Velika Peč, Hudournik, Jelenk, Hleviška Planina, Sivka, Mrzli Vrh, etc.) reach an elevation of up to 1,140 meters above sea-level (the height of Javornik, the highest peak in the Idrija Geopark) and offer breath-taking views from the Alps to the Adriatic Sea.
Geology
The Idrija-Cerkno Hills (situated in western Slovenia) and the Idrija Geopark are characterized by a complex geological structure. However, the area is one of the most geologically researched in Slovenia. The rocks forming the surface of the Idrija Geopark can be dated back to 340–60 million years ago.
Among the oldest are the more than 300-million-year-old dark grey shales and sandstones of the Carboniferous Era. Slightly younger are the quartz sandstones, dolomites and fossil-rich limestones of the Permian Era (273–252 million years ago). These are followed by variegated Scythian rocks of the Lower Triassic (252–251 million years ago). The most frequent rocks from this period include dolomites, marlstones, and various limestones, which cover extensive parts of the Idrija region. Poorly bedded Anisian dolomites and conglomerates are also very common. Steep slopes covered with a shallow layer of poorly fertile soil are typical for this type of rock. In the geological history of the Idrija region, the Lower Triassic was followed by a highly tumultuous period. At the beginning of Upper Anisian, extensive movements began during the region’s Middle Triassic normal tectonic phase. Several tectonic trenches (aulacogens) extending East-West were formed in the Idrija region. In one of these aulacogens, called the “ore deposit trench”, the world-renowned Idrija mercury ore deposit was formed. In this zone of strong normal faults with a vertical displacement of 600 to 900 m, individual blocks were pushed up, while others subsided. Around 750 m of strata were eroded of the upthrown blocks. The Middle Triassic (Anisian), Lower Triassic (Scythian), Permian and partly also Carboniferous rocks were removed. Various Middle Triassic (Ladinian) rocks now lie on other blocks in the ore deposit, i.e. directly on the eroded Carboniferous clastites. In the final phase of the development of the Idrija Middle Triassic tectonic trench, the entire region was covered with marshland in which Upper Ladinian rocks rich in organic materials (locally known as “skonca beds”) began to form. Hydrothermal solutions rich in mercury began to penetrate along the deep faults towards the surface. On their way, they permeated all the older layers, from Carboniferous to older Ladinian rocks. This resulted in the formation of highly diversified, rich epigenetic cinnabar ores. Part of the rich cinnabar solutions and cinnabar gels discharged directly into the marshland, forming exceptionally rich (up to 78% Hg), unusual syngenetic sedimentary cinnabar ores. The final period of Ladinian tectonic events was accompanied by extensive volcanic activity with outpourings of diabase and keratophyre.
After the Middle Triassic (Ladinian and Anisian) tectonic shifts stabilized, Carnian layers (237–227 million years ago) containing varieties of quartz conglomerates and sandstones, including large quantities of limestones and white dolomites, were deposited throughout the entire Idrija region. In the Norian and Rhaetian stages (227–201 million years ago), stromatolitic and oncolitic dolomites known as the main dolomite with rare limestone inclusions appeared in many areas. Jurassic limestones and dolomites can only be found in the Trnovo Forest, south of the Idrija region. These were followed by more or less stratified organogenous Lower (145–100 million years ago) and Upper Cretaceous (100–66 million years) limestones. The sedimentation process in the Idrija region was concluded with Palaeocene-Eocene flysch rocks, which are “only” 66–34 million years old.
Due to the far-reaching consequences of the Tertiary tectonic activity that began 66 million years ago (and was the cause of the rising of the Alps), no normal stratigraphic sequences of rocks can be found anywhere in the Idrija region. During the convergence of the Eurasian and African tectonic plates and the subsequent subduction of the Adriatic microplate under the Eurasian continent in Tertiary, two large geotectonic units were formed in the territory of Slovenia. The western and central parts of Slovenia belong to the External Dinarides, which to the east gradually transition into the Internal Dinarides, while northwestern Slovenia is part of the Southern Alps, which are thrust southwards from the north onto the External Dinarides. Both geotectonic units consist of extensive thrust units with a complex lithostratigraphic structure.
The Idrija region forms part of the External Dinarides, and for this reason has a typical thrust structure. It developed from a large recumbent fold. The strata of the upper limb of the fold are in an inverse position. Owing to further displacements, the fold was cut up into individual large nappes and intermediate thrust slices, which moved in a south-west direction along the thrust fault plane for tens of kilometres. In the deeper basement of the entire Idrija region lies the Hrušica nappe comprised of a range of rocks, form Carboniferous rocks to Palaeocene-Eocene flysch in normal position. Thrust onto the Hrušica nappe is the Koševnik thrust slice, built of Lower and Upper Cretaceous rocks, also in normal position. These are followed by partly normal and partly inverse strata of Upper Triassic (Norian-Rhaetian) dolomites in the Čekovnik thrust slice. These are covered by inverse Carboniferous, Permian, Scythian, Ladinian, and Carnian rocks of the Kanomlja thrust slice. The highest lying thrust unit is the Trnovo nappe comprised of two internal thrust blocks. The lower block is called the Idrija internal thrust block. It is composed of layers of Carboniferous to Norian-Rhaetian rocks in normal and partly inverse position. The mercury ore deposit is located within this structure. The upper internal thrust block is called the Tičnica internal thrust block. It consists of Carboniferous shales to Eocene flysch rocks in normal sequence.
Thrusting and present-day erosion conditions are responsible for extensive levellings and large tectonic windows lying in deeply cut gorges. The Idrijca Valley features the Strug single tectonic window, while the Nikova Ravine features the Bevk single tectonic window. A rare phenomenon in the Southern Alps is a triple tectonic window in the Bratuš ravine in Zgornja Kanomlja. Here the strata of the Čekovnik and Koševnik thrust slice and the rocks of the Hrušica nappe are exposed on the surface below the Kanomlja thrust slice.
Of the numerous faults, let us mention only the two most important ones: the renowned Idrija fault, which runs through Slovenia and can be clearly seen in satellite images. Near Idrija, it is met by the regional Zala fault. In their initial phase, both faults were shaped as normal fault with a vertical component of 480 m. Because of changes in tension, they were reshaped into dip-slip faults. The horizontal component of the movement along the Idrija fault is about 2,500 meters.
A simplified geological map of the Idrija Geopark
Geological map 1 : 50 000 with natural and cultural heritage
Karst
The diverse and frequently unique karst phenomena in the Idrija region are a reflection of the complex geological structure and the tectonic and morphological divergence of the Idrija terrain. The karst terrain of the Idrija region dan be roughly divided into high karst and isolated karst, which covers the non-karst parts of the region.
High karst covers the area of Pevec, Idrijski Log, Zadlog, the central parts of the Črni Vrh Plateau, Predgriže, and Lome, as well as the Godovič part of the Hotedršica Lowlands. Towards the south and west, it reaches the borders of the Trnovo Forest, along with Javornik and Hrušica. Because of geological conditions, high karst transitions into a shallower limestone karst near Zagrebenec, Gladke Skale, and the Nikova Valley. Geologically, high karst and the shallower limestone karts consist of limestones from Lower and Upper Cretacious. High karst is characterized by deep karstified carbonate rocks, predominantly limestones, with classical karst features: sinkholes, limestone pavements, and karrens on the surface; deep chasms and short subhorizontal caves underground; and short subterranean rivers and ponors (“covert karst”) in the dip-slip margins. Notable karst phenomena include the Habečk Abbys, the renowned karst spring of the Wild Lake, and the powerful springs of Podroteja.
The rest of the Idrija region where no high karst is present is formally classified as non-karst terrain. However, karst phenomena (classified as isolated karst) can also be found here as individual occurrences or clusters. Isolated karst usually develops in old limestones and dolomites among impermeable rocks (such as schists and quartz sandstones). The size and development stage of karst phenomena also depend on geological features such as the petrographic character of the rocks, the size of the clearing, the thickness of impermeable rocks, the tectonics, hydrological conditions, and climate. Extensive patches of isolated karst have developed in Idrijske Krnice, the Ledine Plateau, the Vojsko Plateau, and in Srednja Kanomlja.
Watercourses
The largest watercourse in the Idrija Geopark is the Idrijca River with its major tributaries: the Belca, Zala, Nikova, Kanomljica and Trebuščica streams.
Most of the surrounding high karst plateaus feature no larger watercourses as the karstified terrain makes most of the surface running water sink underground. Watercourses are formed for a short time only during heavy rainfall. In a deluge or when the frozen ground does not let water pass to the underground, certain regions of the karst plateaus are become flooded.
Another peculiarity of note is the watershed between the Adriatic and the Black Sea drainage basins. The Adriatic drainage basin covers the Isonzo river system (along with the Idrijca River and its tributaries), while the Black Sea drainage basin covers the Ledine Plateau and the watercourse Žirovnica, which flows into the Sovra, then to the Sava river and all the way to the Danube and the Black Sea.
Climate
The Idrija Geopark has a moderate continental climate. The average temperatures in October are higher than in April. The precipitation regime is sub-Mediterranean with an average annual precipitation of approximately 2,500 millimetres. The highest precipitation is in November (first peak), and the second peak is in spring. The lowest precipitation is in winter (February) and in summer (July). Temperature inversion is a frequent phenomenon in winter as cold air and fog accumulate at the bottom of the region’s basins, leaving areas at higher altitudes with warm and serene weather.
Vegetation
The forests of Idrija are nestled between the Julian Alps in the north and the Trnovo Plateau in the south, in a territory transitioning from the Eastern Alps to the Dinarides.
Almost 79 % of Idrija Geopark is covered in forests, which is well above the Slovenian average. The predominant forest type in the Idrija region is the Dinaric beech and fir forest (Omphalodo-Fagetum).
In terms of the Geopark’s flora, of particular note are Blagay’s Daphne, Alpine Butterwort, Hairy Alpenrose, Twoflower Violet, Scopolia, Hacquetia, Bear’s Ear, Idrija Primrose, Alpine Snowbell, Alpenrose, Lily of the Valley, Common Houseleek, Large Red Dead Nettle, etc.
Population
In 2018, the Idrija Geopark area had a population of 11,730 (approximately 5,890 males and 5,840 females), which made the Municipality of Idrija the 45th most populous municipality in Slovenia. In recent years (including 2018), the number of inhabitants has seen a slight decline. The rate of natural increase in 2018 was negative (the crude birth rate was lower than the crude death rate) and the net migration rate was positive (i.e. more people immigrated to the region than emigrated from it). However, the sum of the rate of natural increase and the net migration rate was still negative, so the population has seen a slight decline.
The average age of the inhabitants in 2018 was 44.8 years, which is higher than the Slovenian average of 43.3 years. In 2018, the population density of the area amounted to 40 inhabitants per km2, which is less than the average state-level population density of 120 inhabitants per km2. The most densely populated part of the Municipality is the area in the Idrijca River Valley, where Idrija and Spodnja Idrija, the two largest settlements of the Idrija Geopark, are located. Both settlements are urban and account for more than half of the population of the Municipality. All other settlements, mostly situated in the surrounding hills or flat karst plateaus, are noticeably smaller.
Economy
Since its origins, the history of Idrija has been closely intertwined with mining. Anthony’s Mine Road, the mine’s main entry point, was opened in 1500, and today, it is open to visitors as a tourist attraction. Ore extraction was carried out until 1987, when the shutdown of the mercury mine began after a decrease in mercury prices in the global market.
After the mine’s closure, Idrija recovered quickly despite having lost a large company. After 1975, a number of smaller companies as well as electrical engineering and metal-processing plants were established, chief among which were Kolektor and Hidria. Both of these large concerns export a considerable share of their output abroad. Another of the larger companies operating within the Idrija Geopark produces air-conditioning devices.
Agriculture was once quite developed in high-altitude areas, on plateaus, despite the large surface inclinations, severe winters, and low-fertility soil. Today, agriculture activities are in decline as fields and meadows are steadily overgrown. Large farms remain only in more favourable locations, while young people seek employment in major towns. In recent years, the Idrija Geopark area has shown an increase in the production of dairy and meat products, along with horse breeding, sheep breeding, and beekeeping. Slovenia’s entry into the European Union in 2004, which leads a favourable agricultural policy, has helped financially support agriculture and preserve the population and cultural landscape even in areas that are less suitable for farming.
One of the most important and recognisable crafts in the Idrija region is lacemaking. Bobbin lacemaking was first undertaken in Idrija in the late 17th century, and spread to the surrounding areas. During Idrija’s mining period, housewives made lace to help support their families. Today, lace is an important and easily recognizable component of the Idrija Geopark’s heritage.
Tourism
The rich technical and cultural heritage left by Idrija’s mercury mine, which operated for 500 years, together with the area’s exceptional natural heritage, provide a good basis for the successful development of tourism.
The Strategy for the Development of Tourism in the Municipality of Idrija 2019–2023 includes a vision for Idrija as a tourist destination:
Idrija is a green, boutique tourist destination with an abundant heritage of global proportions and the know-how to combine the traditions of its past generations with fresh, modern creativity. Visitors to the town broaden the horizons and enjoy peace and numerous recreational activities in the nearby surroundings characterized by a picturesque and pristine natural environment.
In the Strategy for the Development of Tourism in the Municipality of Idrija 2019–2023, the Idrija Geopark is featured as one of the strategy’s four pillars:
- Mercury Heritage – UNESCO World Heritage (interest: history and technology)
- Idrija Lace – UNESCO Intangible Cultural Heritage (interest: art and design)
- Idrija žlikrofi (interest: gastronomy)
- Idrija Geopark – UNESCO Global Geopark (interest: nature and recreation)
Although the Strategy defines the Idrija Geopark as a separate pillar, there is significant cross-collaboration with the other three pillars.
Traffic
Because of its divergent terrain, the Idrija Geopark has a slightly unfavourable traffic position. The main and most travelled road running through the area is a newly reconstructed state mainroad from the direction of Ljubljana, leading through the village of Godovič and descending along the narrow valley of the Zala stream to Idrija. It then goes on through the narrow valley of the Idrijca River in the direction of Cerkno and Tolmin, towards the region of the Isonzo River. This traffic road branches off onto three important regional state roads in the area of the Geopark (towards Ajdovščina, towards Žiri, and through Kanomlja). The Geopark also has an extensive network of narrow local roads.
The area lacks a railroad network. The nearest railroad connections are located in Logatec and Most na Soči.
The closest airport, the Jože Pučnik Ljubljana International Airport at Brnik, is located approx. 80 km from Idrija. The Ronchi dei Legionari Airport, situated in the Friuli-Venezia Giulia region of Italy, is also located 80 km from the Idrija Geopark.
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